It is proposed to study the role of ion gradients in membrane function of bacteria. The role of an electrochemical potential difference of protons (protonmotive force) in sugar transport and ATP synthesis will be investigated. We intend to impose either a pH gradient (inside alkaline) or a membrane potential (inside negative) and study ATP synthesis in E. coli and Streptococcus lactis. A second project will involve the role of protonmotive force on galactoside transport by E. coli and Strept. lactis. Energy-depleted cells of E. coli will be exposed to a membrane potential by addition of valinomycin and the transport of thiomethylgalactoside measured. The possibility of driving sugar transport by a pH gradient will be investigated.